Portage Lake Lift Bridge Rehabilitation

Client:

Service:

Status:

Share This Project

Overview

The Portage Lake Lift Bridge, which connects the cities of Houghton and Hancock, is the heaviest and widest double-deck bridge in the world and only one of its kind in the state of Michigan. The lift span, which can be raised up to 100-ft., features an upper and lower deck. The upper deck carries four lanes of US Highway 41 and M-26. The lower deck originally carried railroad traffic and currently is used for permit vehicles in the summer and as part of the statewide snowmobile trail system in the winter. It is the only bridge in the region connecting Copper Island in the north with the rest of the Keweenaw Peninsula to the south. In an effort to preserve and maintain this vital crossing, the Michigan Department of Transportion (MDOT) turned to trusted bridge engineering firm Modjeski and Masters (M&M) to lead the structural, electrical and mechanical rehabilitation of the massive 269-ft. long, 54-ft. wide lift span.

The project focused primarily on the replacement of the wire ropes which connect the lift span to the counterweight. To successfully accomplish this, M&M performed work during winter months when the bridge could be left in the fully lowered position, with traffic maintained on the upper deck. This also helped to accommodate snow mobile traffic which commonly uses the lower deck during the same season. M&M also implemented homeland security recommendations, provide structural repairs to the operator’s house, and design upgrades to the barrier gates. Implementing the repairs and retrofits with minimal disruption to traffic was very important as this is the only connector for emergency services on each side of the lake.

Preservation of this historic structure is a high priority. The Portage Lake Lift Bridge was completed in 1959 and is the fourth bridge crossing to be built at the site. The bridge replaces two steel swing bridges before it, and supersedes the original 1875 wooden swing bridge. The Portage Lake Lift Bridge is no doubt an iconic structure due to its sheer size, but also its history of connecting two communities. The bridge is a focal point of both communities and is celebrated yearly at the annual Bridgefest which is held on the anniversary of the bridge being opened to traffic. This project also serves as a continuation of M&M’s long-term relationship with MDOT and is representative of our expertise in the preservation, maintenance and rehabilitation of movable bridges.